Term complement-in-production Definition: One of two goods that are produced jointly using the same resource -- that is, the production of one good automatically triggers the production of the other. The terms "joint products" or "by-products" are two terms commonly used for complements-in-production. A complement-in-production is one of two alternatives falling within the other prices determinant of supply. The other is a substitute-in-production. An increase in the price of one complement-in-production causes a increase in supply of the other. Complements-in-production are goods produced jointly from the same resource or input. This typically happens when the resource in question has parts that can be separated into different products. One example is the production of two goods -- beef and leather -- from one resource -- cattle. Another complement in production example is lumber and sawdust, both produced from a single tree.